Laboratory of Physics of Living Matter, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
Institute of Physics, Faculty of Physics, Astronomy and Applied Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100, Torun, Poland.
Sci Rep. 2017 Aug 18;7(1):8852. doi: 10.1038/s41598-017-09482-w.
Contactin-4 (CNTN4) is a complex cell adhesion molecule (CAM) localized at neuronal membranes, playing a key role in maintaining the mechanical integrity and signaling properties of the synapse. CNTN4 consists of six immunoglobulin C2 type (IgC2) domains and four fibronectin type III (FnIII) domains that are shared with many other CAMs. Mutations in CNTN4 gene have been linked to various psychiatric disorders. Toward elucidating the response of this modular protein to mechanical stress, we studied its force-induced unfolding using single molecule atomic force microscopy (smAFM) and steered molecular dynamics (SMD) simulations. Extensive smAFM and SMD data both indicate the distinctive mechanical behavior of the two types of modules distinguished by unique force-extension signatures. The data also reveal the heterogeneity of the response of the individual FNIII and IgC2 modules, which presumably plays a role in the adaptability of CNTN4 to maintaining cell-cell communication and adhesion properties under different conditions. Results show that extensive sampling of force spectra, facilitated by robot-enhanced AFM, can help reveal the existence of weak stabilizing interactions between the domains of multidomain proteins, and provide insights into the nanomechanics of such multidomain or heteromeric proteins.
神经细胞黏附分子 4（Contactin-4，CNTN4）是一种位于神经元细胞膜上的复杂细胞黏附分子（CAM），在维持突触的机械完整性和信号转导特性方面发挥着关键作用。CNTN4 由六个免疫球蛋白 C2 型（IgC2）结构域和四个纤维连接蛋白 III 型（FnIII）结构域组成，这些结构域与许多其他 CAM 共享。CNTN4 基因的突变与各种精神疾病有关。为了阐明这种模块化蛋白质对机械应激的反应，我们使用单分子原子力显微镜（smAFM）和导向分子动力学（SMD）模拟研究了其力诱导的展开。广泛的 smAFM 和 SMD 数据均表明，两种类型的模块具有独特的力-延伸特征，其机械行为明显不同。这些数据还揭示了单个 FnIII 和 IgC2 模块响应的异质性，这可能在 CNTN4 适应不同条件下维持细胞间通讯和黏附特性方面发挥作用。结果表明，机器人增强型 AFM 促进的力谱广泛采样有助于揭示多结构域蛋白域之间存在弱稳定相互作用，并深入了解此类多结构域或异源二聚体蛋白的纳米力学特性。
